Formation and Evolution Mechanisms of Severe Haze Pollution in the Sichuan Basin, Southwest China

Xianyu Yang ； Yaqiong Lu ； Xinsheng Zhu ； Jianjun He ； Qi Jiang ； Kai Wu ； Haolin Wang ； Xiaoling Zhang ； Shigong Wang

《Aerosol and Air Quality Research》 20卷11期 (2020/11) Pp. 2557-2567+ap1-6

https://doi.org/10.4209/aaqr.2020.04.0173

摘要

Severe haze episodes are important environmental issues, and the rapid formation and evolution mechanisms of such episodes over complex terrain remain poorly understood. The Sichuan Basin (SCB) periodically experienced heavy haze pollution during the winter of 2016, with the maximum regional average PM_(2.5) concentration reaching almost 120 μg m^(-3). In this study, we characterize a severe haze episode in the SCB from 20 to 30 January 2017 using comprehensive measurements and model analyses. The evolution of this severe episode shows clear stages, with gradual PM_(2.5) increases under stagnant weather conditions in Stage I (aerosol accumulation stage) and with explosive PM_(2.5) increases mainly associated with cross-border transport from the southern SCB in Stage III (rapid formation stage). The process analysis results indicated that primary emissions and aerosol processes were the major sources of PM_(2.5) in these urban regions, whereas vertical transport and dry deposition generally acted as sinks of PM_(2.5). In the presence of southwesterly synoptic winds, the aerosols emitted from the southern SCB were transported to Chengdu and the surrounding areas through horizontal transport and accounted for 66% of the PM_(2.5) concentration in Chengdu during Stage III. Our results reveal the detailed formation mechanism of a severe haze episode in the SCB under the effects of regional transport and synoptic forcing patterns to improve the understanding of haze formation in areas with complex terrain.

關鍵字

Air quality ； Haze pollution ； Process analysis ； Sichuan Basin